Sealing glass



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INVENTOR. PERRY 7. TIRGDZ United States Patent 3,088,833 SEALING GLASS Perry P. Pirooz, Toledo, Ohio, assigner to wens-Illinois Glass Company, a corporation of Ohio Filed June 6, 1960, Ser. No. 34,223 6 Claims. (Cl. 10G-53) This invention relates to sealing glasses. In a particular aspect the invention relates to low expansion sealing glasses having good fluidity at relatively low temperatures.

A need exists for sealing glasses -for sealing relatively low expansion glass parts to each other or for sealing relatively low expansion :glasses to metals of comparable expansion characteristics. Coupled with the requirement for a relatively low expansion sealing glass, it is desirable that such sealing glasses have fairly low annealing points and be quite iluid at relatively low temperatures so that the hot dip method of application of sealing glass can be employed without heating the parent material being sealed above its annealing point, after the seal is formed during the annealing step of the process.

Accordingly, it is an object of this invention to provide sealing glass compositions having relatively low expansion coeicients, which glasses are suitable for hot dip application at temperatures in the range from about 2000" F. to 1800 F. or lower.

Other objects, as well as aspects and advantages, of the invention, will become apparent from a consideration of the accompanying disclosure and the drawings.

According to the invention, there are provided glass compositions containing from 11 to 29 weight percent PbO, from 18 to 32 percent B202, from 34 to 46 percent Zn0,'from 7 to 14 percent Si02, and from 8 to 16 percent CuO.

The foregoing glass compositions of the invention have fiber softening points of less than l600 C. Glasses consisting essentially of the foregoing components in the foregoing proportions generally have expansion coefficients over the range from 0 to 425 C. of from 45 10-r1 to 65 10'7. They are useful for sealing together glass parts having comparable expansion coeflicients.

In a particular and important embodiment of the invention there are provided glass compositions having annealing points not over about 485 C., thermal expansion coefficients (0 to 425 C.) within the range from 49 10'I to 53 10*'7, and having 14 to 20 weight percent PbO, 19 to 21 weight percent B203, 38 to 42 weight percent ZnO, 10 to 14 weight percent Si02, and 9 to 13 kweight percent CuO. If desired, the glass compositions can contain up to percent of other compatible glass-making oxides, such as up to 5 weight percent CdO or Bi203, or up to 1 weight percent Sb203, As203, or colorants such as CoO.

The latter more narrowly defined glasses set forth in the preceding paragraph as having expansion coefficients from t9-53x107 ind particular application in the sealing of Kovar metal parts or Kovar parts to glass parts. As is well known, Kovar is an alloy having the approximate composition, as follows:

Weight percent Iron 54 Nickel 29 Cobalt 17 Actually, Kovar also contains about 0.5% or less of impurities, mainly manganese, silicon and a very small amount of carbon.

FIGURE 1 shows the expansion curves of the sealing glass of Example I, of a base glass of Example I, and of Kovar metal, while FIGURE 2 shows the expansion curves of sealing glasses of Examples Il and III.

3,088,833 Patented May 7, 1963 ICC As will be seen from FIGURE 1, the expansion curve of Kovar is somewhat difficult to match since it is irregular in contrast to the smooth expansion curve of most glasses. The foregoing glasses, however, very closely match the Kovar metal and have great fluidity at comparatively low temperatures.

The great fluidity at relatively low temperatures exhibited by the sealing glass ycompositions of this invention is due in large part to the presence of the copper oxide. The copper oxide is very important in the compositions because it gives this fluidity without increasing the expansion of glasses having the other components of the invention in the ranges indicated to any significant extent. While silica would contribute more to a lowering of expansion of such glasses, increasing amounts of silica greatly increase the viscosity of the melted glasses and this is disadvantageous, particularly in hot dip applications, as previously explained.

The sealing glasses of the present invention are prepared by normal glass-forming procedures. Glass-making components in powder form are mixed and are melted together in the conventional manner in a platinum crucible in a furnace, usually at a temperature in the range of from about 2000 F. to 2300 F. in order to obtain homogeneous, vitreous glass compositions.

The following examples of representative compositions of the invention are merely illustrative and are not to be considered as limiting the invention.

Example I The following components were melted together in the following proportions to prepare the glass:

Parts by weight Lead silicate PbO, 15% Si02) 60 Flint sand (99.9% S102) 30 Boric acid (98% B203, 2% H2O) 61.2 Zinc oxide l2() Cupric oxide 30 The temperature of melting was about 2100" F. From the above change, it will be seen that the composition of the resulting glass was as follows:

This glass had an annealing point of 476 C. and a ber softening point `of 571 C. Its coeiiicient of expansion over the range from 0 to 425 C. was about 50.2 107, l

while the coefficient of expansion of Kovar over the same range is about 51.3 10-'7.

This sealing glass was employed to seal Kovar metal to a base borosilicate glass having an annealing point of 506 C., a fiber softening point of 710 C., and a coeicient of expansion (0425 C.) of 51.2 10'7.

The Kovar and the borosilicate glass were preheated to about 518 C. and the sealing glass was melted in a platinum Crucible using gas-oxygen cross-fire burners. The sealing glass was heated to about 1800-2000 F. in this manner, and the Kovar and borosilicate glass parts to be sealed were dipped in the molten sealing glass and placed in sealing relationship until the sealing glass solidi# fied on partial cooling, completing the seal. The sealed assembly was then annealed in a furnace maintained at about 518 C., for a period of about 15 minutes, to relieve stresses. Thereafter the assembly was slowly cooled to room temperature. A strong seal with little stress resulted.

If the annealing point of the sealing glass were signicantly above the annealing point of the base glass,

annealing of the sealed parts would have resulted in distortion of the base glass part, as will be understood.

The expansion curves of the solder glass of this examand the sealing glass of Example I, and the stress in the base glass was about 400 p.s.i. compression. Another hot `dip seal was made between the sealing glass of Example I and the borosilicate glass described in Examples ple and of the base glass and the Kovar are shown in II and III, and the measured stress in this seal was 1100 FIG. 1. p.s.i. tension in the borosilicate glass.

Examples 11 and III As will be evident to those skilled in the art, various modifications of this invention can be made or followed The following compositions were prepared 111 a man' in the llight of the foregoing disclosure and discussion ner Slmllar to that descnbed 1n Example I' 10 without departing from the spirit and scope of the dis- Parts by Weight closure or from the scope of the claims.

II IH I Claimi Lead oxide (Pho) 14 A sealing glass composition having a ber softening Boum Oxide (B203) 20 20 point below 600 C., a coeicient of expansion (0-425 Zinc oxide 40 40 15 C.) in the range from 45x10-rl to 65X10-7, and con- Sicon dioxide 10 13 slsting essentially of 11 to 29 weight percent PbO, 18 Copper oxide (CUO) 10 13 to 32 weight percent B202, 34 to 46 weight percent ZnO,

7 to 14 weight percent Si02, and 8 to 16 weight percent The liber softening points of these glasses are well below CuO. 600 C. In Example II the glass had an annealing point 2O 2. A sealing glass `composition having an lannealing of 459 C. and in Example III the glass had an annealing point not over 485 C. `and a thermal expansion copoint of 470 C. In FIGURE 2 the expansion curves of ecient (0-425 C.) in the range from 49 107 to these glasses are plotted to the same scale as in FIGURE 53 X104, said glass consisting essentially of 14 to 20 1. Inspection will show that these glasses also very weight percent PbO, 19l to 21 weight percent B202, 38 to closely match the expansion of Kovar metal. The expan- 42 weight percent ZnO, 10 to 14 Weight percent Si02, 9 sion for glass II in the range of from 0 to 425 C. was to 13 weight percent CuO, said glasses having from 0 to 52.9 10'1 and the expansion coeicient for the glass of not more than 5 weight percent of other compatible Example III was 49.7X10-7. These glasses are also exglass-making oxides. cellent for sealing to Kovar. 3. A sealing glass composition having a fiber softening Hot dip seals were made with each of these solder point below 600 C., a coecient of expansion (0-425 glasses to a borosilicate glass by the hot dip method in C.) in the range from 107 to 65 l07, and cona manner similar to that described in Example I, and the sisting essentially of 11 to 29 weight percent PbO, 18 to room temperature stress in-the base glass was measured. 32 Weight percent B203, 34 to 46 weight percent ZnO, This borosilicate base glass had an annealing point of 7 to 14 Weight percent SiO2, 8 tof16 Weight percent CuO, 557 C., aber softening point of 754 C. and acoeicient 35 and up to 5 weight percent of other compatible glassof expansion (0-425 C.) of 60.4X 10'7. The stress obmaking oxides. tained with sealing glass II was about 300 p.s.i. tension in 4. A sealing glass composition according to claim 1 the borosilicate glass and with sealing glass III was about and consisting essentially of about 17 parts by Weight 1150 p.s.i. tension in the borosilicate glass. o Pb0, about 20 parts by weight B203, about 40 parts by weight ZnO, about 13 parts by weight Si02 and about Examples I VX V1 10 part-s by weight CuO.

In the table below are shown compositions IV to XVI 5 A Soaing glass-composition according to dan? 1 of the invention which have ber softening points below md conslstmg essentlally o f about 20 Parts oy Welght 600 C. and coefficients of expansion (0-425 C.) in the Php about 2o Parts by Welght B 2O3 @bout 4o Parts by range from 46 6X10 v (Example XVI) to 62 8X10.7 weight ZnO,. about 10 parts by weight S102, and about 10 (Example IV). These glasses were all prepared in a man- 45 Parts by Wefght CUO- ner similar to that described in Example I. The table 6' A elmg glas? oomposmon accodmg to Claim 1 Shows the compositions in parts by Weightand consisting essentially of about 14 parts by weight PbO,

Hot -dip seals were made to the same borosilicate glass about 2o Parts by Weight bzobbobt 4o Parts by Wei'gbt set forth in Examples II and III. The measured stress 50 Zn?, about 10 Pans by Welgbt 5102 and about 10 Parts by in the borosilicate iglass is shown in the table for the seals Welgbt CUO- so prepared. Of course, the borosilicate glass employed was not ideally matched to the sealing glass. Neverthe- References Cited m the me of uns patent less, good seals were eiected even though the stress was UNITED STATES PATENTS somewhat undesirably high in some cases. 2,889,952 Claypoole June 9, 1959 2,931,142 Veres Apr. 5, 1960 Example IV V VI VII VIII IX X XI XII XIII XIV XV XVI Pbo 29 23 23 2o i7 2o 14 14 14 11 11 11 ii B203- 20 20 2o 23 26 2o 29 26 26 32 26 26 2o Zno-- a4 40 35 4o 4o 43 40 43 40 40 46 40 4o :3103. 7 7 7 7 7 7 7 7 7 7 7 7 i3 Cuo- 1o 1o ig 1o 10 10 10 1o 13 10 10 16 16 gga'lig'pbi't ""52 46o 472 482 474 468 49o 48o 465 For comparative purposes it is noted that a hot dip seal was also made `between the base glass of Example I FOREIGN PATENTS 634,548 Great Britain Mar. 22, 1950 

1. A SEALING GLASS COMPOSITION HAVING A FIBER SOFTENING POINT BELOW 600$C., COEFFIENENT OF EXPANSION (0-425$ C.) IN THE RANGE FROM 45*X10-**7 TO 65X10-**7, AND CONSISTING ESSENTIALLY OF 11 TO 29 WEIGHT PERCENT PBO, 18 TO 32 WEIGHT PERCENT B2O3, TO 46 WEIGHT PERCENT ZNO, 7 TO 14 WEIGHT PERCENT SIO2, AND 8 TO 16 WEIGHT PERCENT CUO. 